Figure 4
Correlation between MHC II downregulation and SPI-1 or SPI-2 gene expression. Correlation between MHC II downregulation capacity (X-axis) and expression of Salmonella Typhimurium SPI-1 genes hilA (A) and sopB (B) and SPI-2 genes ssrA/B (C) and ssaH (D) (on the respective Y-axes) by different Salmonella strains, with r = Pearson correlation coefficient. Gene expression was measured as the luminescence of the respective Salmonella strain transformed with a plasmid in which the hilA, sopB, ssrA/B or ssaH promoter was cloned upstream of the reporter genes luxCDABE. Luminescence (and expression of the virulence genes) was measured in real time with a Fluoroskan luminometer during 24 h incubation of these strains at 37 °C in LB medium. MHC II downregulation capacity is presented as the average mean FL-5 signal ratios between infected and uninfected porcine alveolar macrophages (PAMinf and PAMuninf, respectively). Gene expression is presented as the average relative luminescence units (RLU) of three independent measurements conducted in triplicate ± standard deviation